Modern electronic organs are capable of producing a wide variety of tonal effects under the control of different voicing tabs, percussion processing circuitry, automatic rhythm systems and the like. As a consequence, it is possible to produce tonal effects which simulate a wide variety of instruments, including wind instruments, strings, and percussion instruments. In addition, through the use of automatic rhythm sections, unique instrumental effects, such as banjo strumming, trilling and the like can be produced.
A unique tonal effect which has been difficult, if not impossible, to produce on prior art electronic organs is the "glide" or "Hawaiian Guitar" gliding tone effect which is produced by commencing the tone slightly flat (usually a semi-tone flat) and then gliding or sliding into proper tuning for the sustained note in a relatively short, but clearly discernible time interval. On the Hawaiian guitar instrument itself, this is not difficult to achieve manually. In a keyboard instrument, however, because of the inherently different nature of the tone selection and control, this effect is quite difficult to produce. In many electronic organs it is not possible to produce. By providing a detuning access control for the musician, it would be possible to play a note with one hand and to manually detune and bring back into tuning the oscillator used to produce such a tone. To achieve a "Hawaiian Guitar" or glissando effect in this manner is quite cumbersome and severely limits the flexibility available to the musician at such a point in a composition because of the necessity for effecting the sliding control with one hand (or a foot) throughout the time interval of the slide.
As a consequence, it is desirable to provide an automatic control for producing a Hawaiian guitar gliding sound, delayed vibrato, or glissando with a minimum of effort on the part of the musician and in a manner which can be effected by even a musician of moderate skill.